onnxruntime

Allow empty shapes and do not validate them for inputs/outputs (#18442)

### Description
Allow empty shapes and do not validate them for inputs/outputs at the
InferenceSession::ValidateInputsOutputs().

### Motivation and Context
https://github.com/microsoft/onnxruntime/pull/17301 disallowed empty
shapes.
However, many models depend on them as a way to pass shapes of different
ranks.